The present disclosure relates to paper transport devices, document transport devices, and image forming apparatuses which include a guide for switching between paper transport paths using a motor.
In an image forming apparatus such as a multifunctional peripheral, a copier, a printer, or a facsimile machine, motors are used to rotate rotary bodies for transporting paper as well as rotary bodies such as drums for forming toner images. In transporting sheets of paper, the torque required for transporting a sheet (the sufficient magnitude of torque which causes no step-out) varies depending on the thickness of the sheet.
For example, a typical image forming apparatus adopts a technique of controlling a current which is caused to flow through a stepping motor according to the thickness of the sheet of paper. Specifically, in this technique, a stepping motor is used to transport-drive the paper. The thickness of a target sheet of paper on which an image is to be formed is detected, and the drive current value for constant-current chopping control, by which the excitation phase of the stepping motor is sequentially switched to obtain a constant drive current, is variably controlled according to whether the target sheet is thick or not. With this configuration, in the case of forming an image on a thick sheet of paper, the current of a necessary and sufficient amount is caused to flow through the motor, to thereby allow the motor to output sufficient torque to transport the sheet without causing step-out.